Least Significant Bit

RSpec is a lot about readability. And its matchers are really a joy to aid you on that. And now it is even easier to add simple matchers for (in David’s own words) you to create your own custom matchers in just a few lines of code when you don’t need all the power of a completely custom matcher object.

Let’s say you want to spec your array is sorted by an attribute on the contained elements, like:

#in your *_spec.rb
it 'should be sorted incrementally' do
  struct_array.should be_sorted_by(:attr)
end

Simple, define a simple matcher and make sure you include in your spec_helper.rb.The trick is the simple matcher returns a boolean that will make expectation pass (returning true of course) or not.

def be_sorted_by(attr)
  simple_matcher("a sorted fixnum array") do |given|
    ary = given.collect { |e| e.send(attr).to_i }
    ary.sort == ary
  end
end

yes, you noticed correctly the to_i in the matcher implementation, well I’ll leave it to you to extend that :-)